There are lots of ways to make a good MDFC, like its power, flavor, or design
While you can use basically any card as your commander still (except for a few choice powerhouses), some are going to be a bit more fun than others
Like most Magic: The Gathering cards, the value of Traveling Chocobo depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Final Fantasy)
Green is good when you need to put lands into the graveyard, my simple solution is a budget land that fetches in Terramorphic Expanse, and the expensive solution is a fetch land like Misty Rainforest
That can save your bacon in many scenarios
It might be that theyve outgrown their playgroup a little, or that the people they play with more regularly dont have access to the same sorts of cards